Fast wireless local area network communication method and apparatus using multiple transfer rate partitioning and cooperative transmission

ABSTRACT

A wireless local area network (WLAN) communication method and apparatus using multiple transmission speed partitioning and cooperative transmission are disclosed. The WLAN communication method includes transmitting, by access point to the nodes, transmission time slots, partitions and internal transmission priorities using transmission time slot information, partition information and internal transmission priority information, receiving uplink packet from one node, determining whether downlink data to be transmitted to the high speed or the low speed node is present, or not in the download queue, transmitting, if present, the downlink packet to the nodes, removing downlink data from the download queue for ACK, and transmitting, if not present, transmitting ACK to the nodes.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation Application of U.S. patentapplication Ser. No. 16/733,466, filed on Jan. 3, 2020, which is aContinuation Application of U.S. application Ser. No. 15/830,568 filedon Dec. 4, 2017, which is a Continuation Application of application Ser.No. 14/450,059 filed on Aug. 1, 2014 now U.S. Pat. No. 9,877,320 issuedon Jan. 23, 2018, and claims the benefit under 35 U.S.C. § 119(a) ofKorean Patent Application Nos. 10-2013-0111671 filed on Sep. 17, 2013and 10-2014-0055079 filed on May 8, 2014, in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a wireless local network(WLAN) communication, and, more particularly, to a technique forincreasing the speed of WLAN communication.

2. Description of the Related Art

WLAN communication is wireless communication technology based on theIEEE 802.11 standard. Although not supporting mobility, the WLANcommunication is widely employed in notebook, smart phone, portablestorage device, camera, etc. because the WLAN can efficiently expand anetwork area wirelessly at a terminal tip of an LAN.

As the number of WLAN-supported devices used in daily life becomesincreasingly larger, various problems occur in terms of transfer rate orwireless quality management.

For example, the IEEE 802.11 standard allows wireless communicationapparatuses to operate at various transfer rates. Nevertheless, sincethe equal opportunity to access a channel is provided to all nodes, theperformance of high speed transmission nodes that access a correspondingWLAN may be considerably deteriorated if a plurality of devices ofrelatively low transfer rates accesses the WLAN. This phenomenon isoften referred to as performance anomaly.

In order to overcome this problem, time fairness approach that assignsproper transmission time slots to respective nodes, taking into accountthe size of data, that is, the length of a transmission queue, thatshould be transmitted by each of the nodes has been proposed.

Furthermore, IEEE 802.11 allows for a plurality of frequency channels.As an increasingly large number of access points and nodes occupy thesame space, frequency collision may occur between access points usingthe same frequency channel. Since a WLAN technology is designed suchthat a transmitting node should receive an acknowledgement signalindicative of the proper reception of data from a receiving node aftertransmitting a packet and then transmit the next packet, data transferrate may be significantly reduced if data is not normally transmittedand received due to frequency collisions.

Meanwhile, a cooperative transmission technique is a communicationtechnique in which a low speed node selects a high speed node as a relaynode and allows the relay node to forward its transmission data, therebyovercoming the problem of low transfer rate.

The cooperative transmission technique incurs overhead because aprocedure in which a low speed node investigates adjacent nodes,searches for and selects a high speed node that will forward data onbehalf of itself, and obtains permission should be undergone. Even ahigh speed node selected for cooperative transmission cannot overcomethe problem of a reduction in transfer rate when a frequency collisionoccurs, and the improvement of performance cannot be achieved as much asexpected if channel access time is not appropriately assigned.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a fast WLAN communication method and apparatususing multiple transfer rate partitioning and cooperative transmission.

In accordance with an aspect of the present invention, there is provideda fast wireless local area network (WLAN) communication method usingmultiple transfer rate partitioning and cooperative transmission, themethod including, by an access point, transmitting transmission timeslot information, partition information and internal transmissionpriority information, used to enable transmission time slots, partitionsand internal transmission priorities to be identified, respectively, tonodes, receiving an uplink packet from any one of the nodes, determiningwhether downlink data to be downloaded to the node is present in adownload queue while waiting for a basic waiting time, if downlink datato be transmitted to the node is present, transmitting a downlink packetrelated to the downlink data to the node after the basic waiting timehas elapsed, if a reception acknowledgement packet is received from thenode after the downlink packet has been transmitted, removing thedownlink data from the download queue and if downlink data to betransmitted to the node is not present, transmitting a receptionacknowledgement packet to the node after the basic waiting time haselapsed.

The partition information may be information about at least onepartition that is configured to include at least one node set to anequal transfer rate by grouping all of the nodes connected to the accesspoint according to transfer rates.

The transmission time slot information may be information about at leastone transmission time slot, which is one of time intervals available fortransmission, assigned to each of the partitions grouped according totransfer rates, within a time period between two consecutive beaconframes broadcasted by the access point to the nodes.

The nodes of each of the partitions may operate so as to transmitpackets in the assigned transmission time slot in a contention manner.

The internal transmission priority information may be information aboutpriorities with which the nodes belonging to any one of the partitionsmay transmit the packets in the assigned transmission time slot in anon-contention manner.

The basic waiting time may be set to be equal to a short interframespace (SIFS). The nodes may include a low speed node being relativelyslow, and a high speed node being relatively fast so as to function asrelay nodes for the low speed node, the uplink packet is receiveddirectly from the high speed node, or via the high speed node from thelow speed node, the downlink data is stored in the download queue so asto be downloaded to one of the low speed node and the high speed node,if the downlink packet is transmitted to one of the low speed node andthe high speed node, the downlink data is removed from the downloadqueue in response to a reception acknowledgement packet received fromone of the low speed node and the high speed node and if the downlinkpacket to be transmitted is not present in the any node of the low speednodes and the high speed nodes, the reception acknowledgement packet istransmitted to one of the low speed node and the high speed node fromwhich the uplink packet was transmitted.

The fast WLAN communication method may further include receiving, by ahigh speed node, which is relatively fast among the nodes, along withthe other high speed node belonging to a same partition, a packet from alow speed node which is relatively slow and connected to the accesspoint, when the high speed node receives the packet from the low speednode, determining whether the high speed node is already set as a relaynode, if the high speed node has been set as the relay node, forwardingthe packet, by the high speed node, after a predetermined basic waitingtime has elapsed, if the high speed node has not been set as the relaynode, setting a scheduled waiting time, obtained by adding to the basicwaiting time an individual waiting time, assigned to each of the highspeed nodes, if the forwarding of the packet from other high speed nodehas been detected by packet listening before the scheduled waiting timehas elapsed, discarding, by the high speed node, the packet receivedfrom the low speed node and if the forwarding of the packet from otherhigh speed node has not been detected by packet listening until thescheduled waiting time has elapsed, forwarding, by the high speed node,the packet after the high speed node has set itself as a relay node.

The individual waiting time may be set to a corresponding internaltransmission priority×a unit waiting time.

The unit waiting time may be set to a value equal to the SIFS; and thescheduled waiting time may be set to (1+the internal transmissionpriority)×the SIFS.

In accordance with another aspect of the present invention, there isprovided a wireless local area network (WLAN) communication apparatuscapable of a fast WLAN communication method using a wirelesscommunication module that can be connected to an access point along withWLAN communication apparatuses having a plurality of different transferrates, the apparatus including a communication control unit configuredto identify transmission time slots, partitions and internaltransmission priorities using transmission time slot information,partition information and internal transmission priority information,respectively, that are received from the access point, to controltransmission/reception of packets via the wireless communication modulealong with the other WLAN communication apparatuses belonging to a samepartition in a specified transmission time slot in a contention manner,or control transmission/reception of packets based on the internaltransmission priorities in a non-contention manner, according to a WLANcommunication standard, to wait for a predetermined basic waiting timeafter transmitting an uplink packet to the access point, then to receivea downlink packet or a reception acknowledgement packet, and to, whenthe downlink packet has been received from the access point, transmit areception acknowledgement packet to the access point after waiting forthe predetermined basic waiting time, and a relay control unitconfigured to, if a packet is received from a relatively slow WLANcommunication apparatus via the communication control unit with requestof relaying the packet and the WLAN communication apparatus is set asthe relay node, wait for the predetermined basic waiting time after thereceiving of the packet from the relatively slow WLAN communicationapparatus and then to forward the packet, configured to, if the WLANcommunication apparatus has not been set as the relay node, set ascheduled waiting time, obtained by adding the basic waiting time and apredetermined individual waiting time, after the reception of the packetfrom the relatively slow WLAN communication apparatus, configured to, ifforwarding of the packet by another WLAN communication apparatusbelonging to a same partition has been detected through packet listeningby the communication control unit before the scheduled waiting timeelapses, discard the packet received by the communication control unitand configured to, if forwarding of the packet by the other WLANcommunication apparatus belonging to the same partition has not beendetected until the scheduled waiting time has elapsed, set the WLANcommunication apparatus as a relay node, and then to forward the packetvia the communication control unit.

The partition information may be information about at least onepartition that is configured to include at least one node set to anequal transfer rate by grouping all of the nodes connected to the accesspoint according to transfer rates.

The transmission time slot information may be information about at leastone transmission time slot, which is one of time intervals available fortransmission, assigned to each of the partitions grouped according totransfer rates, within a time period between two consecutive beaconframes broadcasted by the access point to the nodes.

The nodes of each of the partitions may operate so as to transmitpackets in the assigned transmission time slot in a contention manner.

The internal transmission priority information may be information aboutpriorities with which the nodes belonging to any one of the partitionsmay transmit the packets in the assigned transmission time slot in anon-contention manner.

The relay control unit may be operable to transmit a packet having beenrequested to be uplink-relayed from the relatively slow WLANcommunication apparatus to the access point, to wait for the basicwaiting time, to, if a downlink packet supposed to be transmitted fromthe access point to the relatively slow WLAN communication apparatus isreceived, wait again for the basic waiting time, and to perform relaytransmission of a downlink packet to the relatively slow WLANcommunication apparatus.

The basic waiting time may be set to be equal to a short interframespace (SIFS).

The individual waiting time may be set to an internal transmissionpriority×a unit waiting time.

The unit waiting time may be set to a value equal to the SIFS; and thescheduled waiting time may be set to (1+the internal transmissionpriority)×the SIFS. In accordance with still another aspect of thepresent invention, there is provided an access point device forconnecting an internal network, including low speed nodes beingrelatively slow and high speed nodes being relatively fast so as tofunction as a relay node for the low speed node, the device comprising:a communication module connected to the internal and external networksaccording to a predetermined communication protocol, and a communicationcontrol unit configured to control uplink transmission and receptiondirected to the external network and downlink transmission and receptiondirected to the internal network, and to includes a download queue forstoring downlink data to be transmitted from the external network toeach of the nodes of the internal network, wherein the communicationcontrol unit is operable to: when an uplink packet has been receivedfrom the high speed node or via the high speed node from the low speednode, determine whether downlink data to be download to the high speednode or the low speed node is present in the download queue whilewaiting for a basic waiting time; if downlink data to be download to thehigh speed node or the low speed node is present in the download queue,transmit the downlink packet to the high speed node after the basicwaiting time has elapsed: if a reception acknowledgement packet arereceived from the high speed or low speed nodes after the downlinkpacket has been transmitted, remove the downlink data from the downloadqueue; and if downlink data to be transmitted to the high speed or thelow speed node is not present in the download queue, transmit areception acknowledgement packet to the high speed or the low speed nodeafter the basic waiting time has elapsed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a conceptual diagram illustrating a fast WLAN communicationmethod using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention;

FIG. 2 is a conceptual diagram illustrating division of the transmissiontime slots of each of the partitions in the fast WLAN communicationmethod using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention;

FIG. 3 is a conceptual diagram illustrating internal transmissionpriorities for each of the transmission time slots of high speed nodesin a partition in the fast WLAN communication method using multipletransfer rate partitioning and cooperative transmission according to anembodiment of the present invention;

FIG. 4 is a conceptual diagram illustrating setting of a high speed nodehaving the highest internal transmission priority as a relay node andfirst packet transmission and subsequent packet transmission through theset relay node in the fast WLAN communication method using multipletransfer rate partitioning and cooperative transmission according to anembodiment of the present invention;

FIG. 5 is a conceptual diagram illustrating setting of a subsequentrelay node and the transmission of a packet that are performed when acurrent relay node stops its operation in the fast WLAN communicationmethod using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention;

FIG. 6 is a flowchart illustrating a fast WLAN communication methodusing multiple transfer rate partitioning and cooperative transmissionaccording to an embodiment of the present invention;

FIG. 7 is a block diagram illustrating a WLAN communication apparatuscapable of fast WLAN communication using multiple transfer ratepartitioning and cooperative transmission according to an embodiment ofthe present invention;

FIG. 8 is a conceptual diagram illustrating the downlink transmission ofan access point AP using multiple transfer rate partitioning andcooperative transmission according to an embodiment of the presentinvention;

FIG. 9 is a flowchart illustrating a fast WLAN communication methodcapable of increasing the amount of downlink transmission of an accesspoint using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention;

FIG. 10 is a conceptual diagram illustrating downlink relay transmissionof an access point and a relay node using multiple transfer ratepartitioning and cooperative transmission according to an embodiment ofthe present invention;

FIG. 11 is a flowchart illustrating a fast WLAN communication method forincreasing the amount of downlink relay transmission of an access pointand a relay node using multiple transfer rate partitioning andcooperative transmission according to an embodiment of the presentinvention; and

FIG. 12 is a block diagram illustrating an access point device capableof increasing the amount of downlink transmission using multipletransfer rate partitioning and cooperative transmission according to anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Specific structural and functional descriptions of the embodiments ofthe present invention described herein are given as examples merely toillustrate the embodiments of the present invention. Embodiments of thepresent invention may be implemented in various ways, and the presentinvention should not be construed as being limited to the embodimentsdescribed herein.

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings. The same reference numeralsare assigned to the same components through the drawings, and redundantdescriptions of the same components of the drawings will be omitted.

FIG. 1 is a conceptual diagram illustrating a fast WLAN communicationmethod using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention.

Referring to FIG. 1, the fast WLAN communication method using multipletransfer rate partitioning and cooperative transmission can reduceperformance anomaly and frequency collisions through the combination ofa multiple transfer rate partitioning technique and a cooperativetransmission technique that have different purposes and effects.

In FIG. 1, a plurality of nodes 111 to 123 having different transferrates is connected to an access point AP 11. It is assumed that somenodes of the nodes 111 to 122 are high speed nodes 111 to 118 that havebeen set to relatively high transfer rates, other nodes are intermediatespeed nodes 119 to 121 that have been set to intermediate transferrates, and the rest are low speed nodes 122 and 123 that have been setto relatively low transfer rates.

At least one partition including at least one node which has been set tothe similar transfer rates is configured by grouping, based on thetransfer rates, the nodes 111 to 123 connected to the access point 11.

For example, among the high speed nodes 111 to 118 whose transfer rateshas been set relatively high, some nodes 111 to 113 may constitute afirst partition 21, some other nodes 114 to 116 may constitute a secondpartition 22, and some other nodes 117 and 118 may constitute a thirdpartition 23.

The intermediate speed nodes 119 to 121 whose transfer rate has been setintermediate constitute a fourth partition 24.

The low speed nodes 122 and 123 whose transfer rate has been setrelatively low may constitute independent partitions, respectively.However, in accordance with the WLAN communication method of the presentinvention, using the cooperative transmission technique, the low speednode 123 whose transfer rate had been set low, having constituted aanother partition 26, may request the first partition 21 to relay, andthen may be merged with the first partition 21.

A WLAN access point 11 based on IEEE 802.11 outputs beacon framescarrying information about a network at beacon frame intervals.

Operations occurring with respect to uplink traffic in partitions 21 to26 are described as follows.

During a time period between two consecutive beacon frames, thepartitions 21 to 26, divided respectively based on the transfer rates,are allocated to transmission time slots based on the transfer rates.The high speed or low speed nodes 111 to 113, 114 to 116, 117 and 118,119 to 121, 122, and 123 belonging to the respective partitions 21, 22,23, 24, 25, and 26 transmit packets within the allocated transmissiontime slots.

Meanwhile, a plurality of partitions 21 to 23 to each of which has beenallocated to the same transmission time slot, due to the same transferrate may sequentially occupy each part of the transmission time slotaccording to a predetermined sequence, for example, according toassigned partition numbers, in a non-contention manner without competingwith one another.

Further, in an embodiment, the high speed nodes 111 to 113, 114 to 116,and 117 and 118 belonging to the same one among the partitions 21 to 26may be assigned with transmission sequence from the access point 11 soas to transmit the packets in the sequence of transmission within eachof the allocated transmission time slots in a non-contention manner.

In another embodiment, the high speed nodes 111 to 113, 114 to 116, 117and 118 belonging to the same one among the partitions 21 to 26 may usechannels in a contention manner within each of the allocatedtransmission time slots according to a distributed coordination function(DCF) defined in IEEE 802.11.

Meanwhile, using a cooperative transmission technique, the low speednode 123 belonging to the sixth partition 26, whose transfer rate is arelatively low, may request the first partition 21, to which the one ormore high speed nodes 111 to 113 belong, to relay a packet, in thetransmission time slot allocated to the sixth partition 26 of the lowspeed node 123.

The low speed node 123 selects any one partition 21 of the partitions 21to 24 having relatively high speed as a relay partition, instead ofconsuming time in selecting a node, to which the relaying of a packetwill be requested, among the high speed nodes 111 to 118, and thentransmits the packet to all the high speed nodes 111 to 113 of thecorresponding partition 21 during the transmission time slot allocatedto the sixth partition 26 to which the low speed node 123 belongs.

The high speed nodes 111 to 113 constituting the partition 21 arerequested to transmit the packet by receiving the packet to be relayedfrom the low speed node 123, or a source node. One of the high speednodes 111 to 113 constituting the partition 21 operate as the relaynode. The high speed node 111 set as the relay node forwards the firstpacket and its subsequent packets, received from the low speed node 123for the purpose of relaying, to a destination node via the access point11.

In other words, all of the high speed nodes 111 to 113 constituting thepartition 21 set as the relay partition receive the packet to be relayedfrom the low speed node 123, but only the high speed node 111, one at atime, selected as the relay node from among the high speed nodes 111 to113 according to predetermined criteria, forwards the packet to adestination node via the access point 11.

Specifically, each of the high speed nodes 111 to 113 discards its ownpacket if the packet received at the same time for the purpose ofrelaying from the low speed node 123 has been forwarded by any otherhigh speed node. In contrast, if the high speed node previouslyoperating as the relay node or the other high speed nodes has notforwarded the packet within a predetermined time, each of the high speednodes 111 to 113 may set itself as the relay node, and then forwards thepacket.

More specifically, although the configuration of the partition 21changes, each of the high speed nodes 111 to 113 constituting thepartition 21 cannot become aware of the change in real time, andtherefore each of the high speed nodes 111 to 113 cannot determine inreal time whether another high speed node having a higher priority thanthe node itself can function as the relay node.

However, if each of the high speed nodes 111 to 113 constituting thepartition 21 is performing packet listening, the high speed node 111,112 or 113 can determine whether another high speed node having a higherpriority than the node itself has forwarded the packet, and can alsodetermine whether cooperative transmission has been completed.

Typically, communication nodes based on IEEE 802.11, after transmittinga packet, wait for a short interframe space (SIFS) time, and thenreceive a reception acknowledgement signal (ACK). This is designed fortaking into account various delay times required to complete thetransmission of a packet and to prepare for receiving a subsequentsignal. Accordingly, each communication node supporting IEEE 802.11transmits its packet, waits for the SIFS time, and then performs anotheroperation.

Exploiting this technique, according to the invention, the high speednodes 111 to 113 may wait for predetermined individual waiting time, andmay detect whether another high speed node has forwarded the packetbefore the individual waiting time elapses.

First, if the low speed node 123 transmits the packet to a relaypartition, all of the high speed nodes 111 to 113 belonging to the relaypartition receive the packet from the low speed node 123. Each of thehigh speed nodes 111 to 113 waits and performs listening to other highspeed nodes forwarding the requested packet during a waiting time,ranging from a basic waiting time of at least 1*SIFS to a scheduledwaiting time which is obtained by adding individual waiting time of eachof the high speed nodes to the basic waiting time.

According to an embodiment, each of the individual waiting times may begiven as, for example, internal transmission priority×unit waiting time.More specifically, the unit waiting time may be set as SIFS forconvenience, although the unit waiting time may be suitably givenaccording to design.

If a high speed node 111 with the highest priority operates normally inthe relay partition, the high speed node 111 operates as a relay nodeand performs packet forwarding.

Although one high speed node 111 among the high speed nodes 111 to 113in the relay partition 21 has been assigned with highest priority, if,for example, the low speed node 123 has successfully forwarded thepacket via the high speed node 112, it may be not necessary to changethe relay node to the high speed node 111. Accordingly, the high speednode 111, with the highest priority but without being designated as arelay node, just waits and performs listening during at least thescheduled waiting time, obtained based on, for example, the relationshipof the following Equation 1, for example, during a scheduled waitingtime of 2×SIFS. If packet forwarding has not been detected until thescheduled waiting time elapsed, the high speed node 111 sets itself asthe relay node at last, and forwards the requested packet.

Basic waiting time=1*SIFS

Unit waiting time=1*SIFS

Individual waiting time=internal transmission priority×unit waiting time

Scheduled waiting time=basic waiting time+individual waitingtime=(1+internal transmission priority)×SIFS   (1)

In Equation 1, the unit waiting time is given as 1*SIFS as an example,in which case an existing SIFS parameter may be used without introducinganother delay time parameter. According to an embodiment, the unitwaiting time may be set using an existing delay time parameter or a newdelay time parameter without using the SIFS parameter.

If, as a result of the listening during the scheduled waiting time, thehigh speed node 113 having the next highest priority has detected thepacket forwarding by the high speed node 111 having a higher priority,or by the high speed node node 112 currently set as the relay node, thehigh speed node 113 discards the packet having been received from thelow speed node 123. If, as a result of the listening during thescheduled waiting time, that is, at least the basic waiting time+theindividual waiting time=1*SIFS+the internal transmissionpriority*SIFS=3*SIFS, the high speed node 113 having the next highestpriority has not detected the packet forwarding by the high speed node111 or 112 having a higher priority, the high speed node 113 sets itselfas the relay node at the time at which a scheduled waiting time of3*SIFS has elapsed, and forwards the requested packet.

During a relaying operation that is performed after the high speed node113 has set itself as the relay node, the high speed node 113 does notneed to listen to another high speed node 111 or 112 performing relayingany longer, and thus the high speed node 113 immediately forwards thereceived packet after receiving the packet from the low speed node 123and then waiting for the basic waiting time of 1*SIFS. When a packet isreceived from the low speed node 123 later, each of the other high speednodes 111 and 112, however, preparing for inability of the high speednode 113 as the relay node, listens for an individual waiting time=itscorresponding internal transmission priority*the unit waiting timeadditionally after the basic waiting time, in order to be aware whetherthe high speed node 113 forwards the packet during the basic waitingtime of 1*SIFS, or that any other high speed node 111 or 112 is newlyset as the relay node and then initiates the packet forwarding.

In other words, each of all the high speed nodes 111 to 113 of thepartition 21, which receive a packet to be relayed from the low speednode 123, waits and performs packet listening for a scheduled waitingtime, that is, the basic waiting time+the individual waitingtime=1*SIFS+its internal transmission priority*the unit waitingtime=(1+its internal transmission priority)*SIFS, based on the internaltransmission priorities assigned to the respective high speed nodes 111to 113, then discards the packet it has received from the low speed node123 and stops the listening, as long as the node itself is not currentlyset as the relay node.

Each of all the high speed nodes 111 to 113, however, sets itself as therelay node right after elapsing of the scheduled waiting time, that is,the basic waiting time+the individual waiting time=1*SIFS+the internaltransmission priority*the unit waiting time, and then forwards thereceived packet, if, through the listening, it has not detected thepacket forwarding from any other high speed node until the scheduledwaiting time has elapses.

Examples of changes in assignment of relay nodes include power failureof high speed node 111 performing relaying tasks in a present beaconperiod, weakening of RF power, or getting out of the partition 21.

Meanwhile, configuration of the partitions and internal transmissionpriorities may continuously change after each beacon period. Withexpiration of a previous beacon period and beginning of a new beaconperiod, another high speed node 112, other than the previous node, maybe provided with the highest internal transmission priority. In thiscase, the high speed node 112, instead of the high speed node 111 thathad performed the relaying operation in the previous beacon period, mayresume a relaying operation of forwarding a packet received from the lowspeed node 123.

In this case, as described above, all of the high speed nodes 111 to 113of the partition 21 has already received the to-be-relayed packet fromthe low speed node 123, and thus the high speed node 112 newly set asthe relay node may immediately forward the received packet to adestination node via the access point 11.

In this manner, the low speed node 123 may rapidly transmit packetsduring a transmission time assigned to the slow nodes having lowtransfer rates via the high speed node 111.

Furthermore, since the high speed nodes 111 to 113 are configured tooperate in such a smart manner that it autonomously designates itself asthe relay node or discards the to-be-relayed packet, based on theirinternal transmission priorities within the partition, necessarily givenby the access point 11 and their scheduled waiting times, it is possibleto implement a cooperative transmission technique without using acomplicated and cooperative relay node selection algorithm. Since theSIFS time is merely, for example, several to ten-odd μs, the delaycaused by further waiting of the high speed node for a plurality of SIFStimes is negligible compared to the benefit from relaying packetsthrough a high speed node, instead of a low speed node.

Furthermore, the access point 11 may revoke extra transmission time slotassigned to the partition 26 of the low speed node 123, and may extendthe length of a transmission time slot to be assigned to the partitions21 to 24 having high transfer rates, resulting in improvement in overalltransmission performance.

Furthermore, since only the limited number of the nodes 111 to 123forming a partition may attempt transmission in a contentious ornon-contentious manner within a limited transmission time slot,collision delay considerably reduces in the corresponding wirelessnetwork and the possibility of frequency collision between otherwireless networks also significantly reduces, compared to a conventionalcase where all nodes within a network or a plurality of nodes having thesame transfer rate attempts transmission within a limited transmissiontime slot in a contention or non-contention manner.

The above operation may be illustrated in conjunction with the drawingsbelow. Although the technical field of a WLAN has been chiefly describedas an example, the spirit of the present invention may be easily appliedto other wireless communication technologies similar to the WLAN of IEEE802.11.

Next, operations that are performed in connection with downlink trafficvia which data is downloaded to a specific node of a specific partitionvia the access point 11 from the outside are described.

Normally, in a WLAN environment, uplink traffic and downlink traffic arepresent in a mixed manner. Since an access point is considered asanother single wireless node, a problem occurs that downlink traffic forforwarding data, externally received by the access point, to a specificnode of a specific destination partition should be also processed withina transmission time slot that is assigned in the same manner as otherpartitions.

Accordingly, the fast WLAN communication method using multiple transferrate partitioning and cooperative transmission according to anembodiment of the present invention gives the access point 11 thepriority to downlink transmission to a specific node whenever the accesspoint 11 performs uplink transmission from the specific node to theoutside, thereby improving the downlink traffic of the access point 11.

More specifically, when an uplink packet to be transmitted to theoutside is transmitted to the access point 11 from a high speed node(for example, the high speed node 111), the WLAN access point 11transmits the transmitted uplink packet to the outside, and determineswhether there is downlink data to be downloaded to the high speed node111 in a download queue. If there is downlink data to be transmitted tothe high speed node 111, the access point 11 transmits the downlinkpacket to the high speed node 111 prior to uplink transmission of theother nodes.

For example, the access point 11, prior to the high speed nodes 111 andetc., waits only for the basic waiting time, that is, 1*SIFS, and thentransmits the corresponding downlink packet to the high speed node 111.

Typically, the high speed node 111 that has transmitted the uplinkpacket to the access point 11 expects the reception of an ACK packet asa result of the packet transmission. In the above case, the high speednode 111 receives a downlink packet instead of an ACK packet. In otherwords, the access point 11 transmits a downlink packet instead of an ACKpacket.

Furthermore, if there is no downlink data to be downloaded from theaccess point 11 to the high speed node 111, when an uplink packet to betransmitted to the outside is transmitted to the access point 11 fromthe high speed node 111, the access point 11 transmits an ACK packet,responsive to the uplink packet, to the high speed node 111.

The high speed node 111 transmits an uplink packet to the access point11, and then receives an ACK packet or a downlink packet from the accesspoint 11 after waiting for 1*SIFS. In any case, it may be possible tocheck whether the uplink packet, transmitted from the high speed node111 itself to the access point 11, has been properly received by theaccess point 11.

Furthermore, if the high speed node 111 normally receives the downlinkpacket from the access point 11, the high speed node 111 transmits anACK packet to the access point 11 after waiting for 1*SIFS.

The access point 11 may remove the downlink data from the download queueafter receiving the ACK packet from the high speed node 111.

In a similar manner, downlink traffic related to the low speed node 123can be improved upon cooperative transmission.

The high speed node 111 set as the relay node for the low speed node 123may transmit an uplink packet, relayed from the low speed node 123 tothe outside, to the access point 11.

After only waiting for the basic waiting time, that is, 1*SIFS, the highspeed node 111 may receive a downlink packet, to be downloaded to thelow speed node 123 or to high speed node 111 itself, or an ACK packet,responsive to the previously transmitted uplink packet, from the accesspoint 11.

In the case, the WLAN access point 11, when receiving the uplink packetto be transmitted to the outside from the low speed node 123 via thehigh speed node 111, transmits the transmitted uplink packet to theoutside, and determines whether the downlink data to be downloaded to atleast one of the low speed node 123 and the high speed node 111 ispresent in a download queue. If the downlink data to be transmitted tothe one of the low speed node 123 and the high speed node 111 ispresent, the access point 11 waits for the basic waiting time, that is,1*SIFS, and then transmits the downlink packet prior to another node.

If the downlink data to be downloaded to the one of the low speed node123 and the high speed node 111 is not present, the access point 11 maytransmit the ACK packet to the low speed node 123 and the high speednode 111 as an acknowledgement of the reception of the uplink packet.

Thereafter, if the high speed node 111 normally receives the downlinkpacket to be transmitted to the low speed node 123 from the access point11, the high speed node 111 waits only for the basic waiting time, thatis, 1*SIFS, and then relays the downlink packet to the low speed node123.

The low speed node 123 receives the downlink packet through the relayingof the high speed node 111, and may then transmit the ACK packetdirectly to the access point 11, without the relaying of the high speednode 111, after waiting for the basic waiting time, that is, 1*SIFS.

The access point 11 may remove the downlink data from the download queueafter receiving the ACK packet from the low speed node 123.

FIG. 2 is a conceptual diagram illustrating the division of thetransmission time slot of each of the partitions in the fast WLANcommunication method using multiple transfer rate partitioning andcooperative transmission according to an embodiment of the presentinvention.

Referring to FIG. 2, two beacon periods are illustrated between threeconsecutive beacon frame signals. Each of the beacon periods has threetransmission time slots for partitions having high speed transfer rates,intermediate transfer rates and low speed transfer rates, respectively.

Furthermore, one or more partitions having the same transfer rate thatshould share each of the transmission time slots may occupy at leastpart of the transmission time slot in a contention or non-contentionmanner.

If the partitions occupy the transmission time slot in a non-contentionmanner, the partitions may be, for example, provided with occupationsequence according to the partition numbers in the transmission timeslot.

FIG. 3 is a conceptual diagram illustrating internal transmissionpriorities for each of the transmission time slots in the fast WLANcommunication method using multiple transfer rate partitioning andcooperative transmission according to an embodiment of the presentinvention.

Referring to FIG. 3, in an n-th beacon period, high speed nodes A, B andC belonging to a specific partition have been given internaltransmission priorities, in the order of high speed node A, high speednode C and high speed node B, respectively, by the access point AP.

In an (n+1)-th beacon period, the high speed nodes A, B and C have beengiven reordered internal transmission priorities, respectively, in theorder of high speed node B, high speed node A and high speed node C.

These internal transmission priorities are used as criteria forselecting a relay node, among high speed nodes, that will performcooperative transmission when the cooperative transmission is requestedby a low speed node.

FIG. 4 is a conceptual diagram illustrating the setting of a high speednode having the highest internal transmission priority as a relay node,and first packet transmission and subsequent packet transmission throughthe set relay node in the fast WLAN communication method using multipletransfer rate partitioning and cooperative transmission according to anembodiment of the present invention.

Referring to FIG. 4, illustrated is a technique for a low speed node,which is a source node of packets and wants to transmit packets to adestination node, to facilitate a high speed node connected to the sameaccess point as a relay node.

The low speed node, that is a source node, requests cooperativetransmission through transmitting to-be-relayed packet to all of thehigh speed nodes, during a transmission time slot when the low speednode occupies a transmission channel. Of course, an optional procedureof the low speed source node transmitting a request to send (RTS) packetand then receiving a clear to send (CTS) packet to the high speed nodesmay precede the transmission of the to-be-relayed data packet.

If the packet had been received from the low speed node at the highspeed nodes, each of the high speed nodes performs packet listeningadapted to detect whether any other high speed node performs theforwarding of the packet, while waiting for a corresponding scheduledwaiting time, that is, the basic waiting time+a corresponding individualwaiting time=1*SIFS+a corresponding internal transmission priority*theunit waiting time=(1+the internal transmission priority)*SIFS,immediately after the reception of the packet. Since no high speed nodeis operating as a relay node in current situation, a high speed nodehaving an internal transmission priority of “1”, or highest priority,sets itself as a relay node at the time at which a scheduled waitingtime of 2*SIFS has elapsed, and then, as a relay node, immediatelyforwards the packet to the destination node via the access point.

It is expected that another high speed node having a priority of “2”performs listening while waiting for a corresponding scheduled waitingtime, that is, the basic waiting time+a corresponding individual waitingtime=1*SIFS+a corresponding internal transmission priority*the unitwaiting time=3*SIFS. However, since forwarding the packet from the highspeed node having a priority of “1” is detected during a third SIFS, thehigh speed node having a priority of “2” discards the packet receivedfrom the low speed node at the time at which a scheduled waiting time of3*SIFS has elapsed.

Meanwhile, each of the nodes may receive an ACK signal output from thedestination node, may wait for a DCF interframe space (DIFS) time, andmay attempt the next transmission of a subsequent packet.

After the high speed node having a priority of “1” has been set as arelay node, the low speed node that is a source node may also transmit apacket to be newly relayed to all of the high speed nodes of thepartition after waiting for a random back-off delay time according tothe IEEE 802.11 standard. Next, the high speed node having a priority of“1” performs the packet forwarding as a relay node after waiting onlyfor a basic waiting time of 1*SIFS, instead of waiting for a scheduledwaiting time, that is, the basic waiting time+a corresponding individualwaiting time=1*SIFS+a corresponding internal transmission priority*theunit waiting time=(1+the internal transmission priority)*SIFS=2*SIFS. Inthis case, the high speed node having a priority of “2” also hasreceived the packet from the low speed node that is a source node. It isscheduled that the high speed node having a priority of “2” performslistening during a corresponding scheduled waiting time, that is, thebasic waiting time+a corresponding individual waiting time=1*SIFS+acorresponding internal transmission priority*the unit waitingtime=(1+the internal transmission priority)*SIFS=3*SIFS. However, if thehigh speed node having a priority of “1” that is a relay node normallyperforms the packet forwarding, the packet forwarding by the high speednode having a priority of “1” is detected in a time period of a secondSIFS, and therefore the high speed node having a priority of “2”discards the packet received from the low speed node at that detection.

FIG. 5 is a conceptual diagram illustrating the setting of a subsequentrelay node and the transmission of a packet that are performed when acurrent relay node stops its operation in the fast WLAN communicationmethod using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention.

Referring to FIG. 5, a partition includes a plurality of high speednodes. Among these high speed nodes, some high speed nodes adjacent to alow speed node that is a source node include a high speed nodepreviously set as a relay node and high speed nodes having internaltransmission priorities of “2” and “4,” respectively.

When the incumbent relay node receives a packet from the low speed node,the incumbent relay node waits only for a basic waiting time of 1*SIFS,and then performs the packet forwarding.

Similarly, it is expected that when the high speed nodes having internaltransmission priorities of “2” and “4” receive the packet from low speednode, these high speed nodes perform packet listening while waiting fora scheduled waiting time of 3*SIFS or 5*SIFS regardless of the presenceor operation of the existing relay node.

Since the existing relay node performs the packet forwarding immediatelyafter the basic waiting time of 1*SIFS has elapsed, the high speed nodeshaving internal transmission priorities of “2” and “4” detect the packetforwarding during a time period of second SIFS, and discard the packetreceived from the low speed node.

If a network environment has changed and then the previous relay nodehas moved out of the partition, when the high speed nodes havinginternal transmission priorities of “2” and “4” receive a packet fromthe low speed node it is scheduled that high speed nodes also performthe packet listening while waiting for the scheduled waiting time of3*SIFS or 5*SIFS, that is, the basic waiting time+a correspondingindividual waiting time, regardless of the presence or operation of theexisting relay node.

If the high speed node having an internal transmission priority of “2”has not detected the packet forwarding during the scheduled waitingtime, that is, the basic waiting time +a corresponding individualwaiting time=1*SIFS+a corresponding internal transmission priority*theunit waiting time=(1 +the internal transmission priority)*SIFS=2*SIFS,the high speed node becomes aware of the operation failure of theprevious relay node. If the high speed node having an internaltransmission priority of “2” has not detected the packet forwarding evenduring a time period of 3*SIFS in which the high speed node havingpriority of “1” is expected to perform the forwarding of the packet, thehigh speed node having priority of “2” becomes aware that the high speednode having priority of “1” does not operate as a relay node, too.

Thereafter, the high speed node having an internal transmission priorityof “2” performs the packet forwarding and, at the same time, sets itselfas a relay node.

If the high speed node having an internal transmission priority of “5”detects the packet forwarding by the high speed node having an internaltransmission priority of “2” immediately after the time period of3*SIFS, that falls within its own example scheduled waiting time, haselapsed, the high speed node having an internal transmission priority of“5” stops packet listening, and then discards the received packet.

FIG. 6 is a flowchart illustrating a fast WLAN communication methodusing multiple transfer rate partitioning and cooperative transmissionaccording to an embodiment of the present invention.

Referring to FIG. 6, in the fast WLAN communication method usingmultiple transfer rate partitioning and cooperative transmission, first,at step S61, the high speed nodes 111 to 118 and the low speed nodes 121to 123 identify individually transmission time slots, partitions andinternal transmission priorities based on a transmission time slotinformation, a partition information and an internal transmissionpriority information received from the access point 11.

The partition information is an information about at least one partitionthat is configured to include at least one node set to the equaltransfer rate, by grouping every node 111 to 123 connected to the accesspoint 11 according to transfer rates.

The transmission time slot information is an information about at leastone transmission time slot, as one of time intervals available fortransmission within a time period between two consecutive beacon frames,assigned to each of the partitions 21 to 26 grouped according totransfer rates.

The nodes 111 to 113, 114 to 116, 117 and 118, 119 to 121, 122, and 123belonging to partitions, respectively, may transmit respective packetsin the assigned transmission time slot in a contention or non-contentionmanner.

Furthermore, the internal transmission priority information is aninformation about priorities with which the nodes 111 to 113, 114 to116, 117, and 118 belonging to any one of the partitions 21 to 26 maytransmit the packets in the assigned transmission time slot in anon-contention manner.

Meanwhile, at step S62, the high speed node 111 to 118 receives packetsfrom the low speed node 122 or 123 connected to the access point 11along with other high speed nodes belonging to the same partition forthe cooperative transmission.

At step S63, the high speed node 111 to 118 determines whether it hasbeen already set as a relay node at the time of the high speed nodes 111to 118 receiving packets from the low speed node 122 or 123. Accordingto the result, the process proceeds to step S64 if the high speed node111 to 118 has already been set as a relay node, while the processproceeds to step S65 if the high speed node 111 to 118 has not yet beenset as a relay node.

If it is determined at step S63 that a high speed node having receivedpackets from a low speed node has been set as a relay node, the highspeed node set as a relay node may wait for a predetermined basicwaiting time, for example, 1*SIFS, after receiving the packet from thelow speed node and then perform the packet forwarding at step S64.

If it is determined at step S63 that the high speed node having receivedpackets from the low speed node has not been set as a relay node, thehigh speed node may set a scheduled waiting time, by adding the basicwaiting time to a corresponding individual waiting time (for example,assigned to each of the high speed nodes according to internaltransmission priorities), at step S65 after receiving packets from thelow speed node.

More specifically, the scheduled waiting time may be set as by thefollowing equation: the scheduled waiting time=the basic waiting time+anindividual waiting time=1*SIFS+a corresponding internal transmissionpriority*the unit waiting time=(1+the internal transmissionpriority)*SIFS.

At step S66, when the corresponding high speed node has detected thepacket forwarding by another high speed node before the scheduledwaiting time elapses through packet listening adapted to detect whetherany other high speed node performs the packet forwarding, thecorresponding high speed node discards the packet received by itself.

At step S67, when the corresponding high speed node has not detected theforwarding of the packet by another high speed node until the scheduledwaiting time has elapsed through packet listening, the correspondinghigh speed node sets itself as a relay node, and then performs thepacket forwarding.

If the packet has been discarded at step S66 or if the packet forwardinghas been performed at step S67, the high speed node may receive an ACKsignal from a destination node after the SI FS time has elapsed. Afterthe ACK signal has been received and the SIFS time has elapsed, the highspeed node becomes ready to transmit its own packet or to newly receivea packet to be relayed from the low speed node.

FIG. 7 is a block diagram illustrating a WLAN communication apparatuscapable of fast WLAN communication using multiple transfer ratepartitioning and cooperative transmission according to an embodiment ofthe present invention.

Referring to FIG. 7, the WLAN communication apparatus 70 may include acommunication control unit 71, a relay control unit 72, a parameterstorage unit 73, and a wireless communication module 74.

The communication control unit 71 controls the transmission andreception of a packet via the communication module 74 according to aWLAN communication standard.

More specifically, the communication control unit 71 identifies atransmission time slot, a partition, and an internal transmissionpriority based on a transmission time slot information, a partitioninformation, and an internal transmission priority information receivedfrom the an access point 11, respectively. Further, the communicationcontrol unit 71 controls the transmission and reception of packets,according to the WLAN communication standard, via the wirelesscommunication module 74 along with other WLAN communication apparatusesbelonging to the same partition in specified transmission time slot in acontention manner, or controls the transmission and reception of packetsvia the wireless communication module 74 based on internal transmissionpriorities in a non-contention manner.

Further, the communication control unit 71 may wait for a predeterminedbasic waiting time, for example, 1*SIFS time, after transmitting anuplink packet to the access point 11, and may then receive a downlinkpacket or an ACK packet from the access point 11, responsive toreception of the uplink packet by the access point 11.

In this case, when receiving a downlink packet related to acorresponding WLAN communication apparatus from the access point 11, thecommunication control unit 71 may wait for the predetermined basicwaiting time, for example, 1*SIFS time, and may then transmit an ACKpacket to the access point 11.

The relay control unit 72, responsive to reception of packets andrequest of the packet relaying from a relatively low speed WLANcommunication apparatus, via the communication control unit 71, waitsfor the predetermined basic waiting time, for example, 1*SIFS time, andthen performs the packet forwarding via the communication control unit71 if a setting as the relay node has been already made. If a setting asthe relay node has been already made, the relay control unit 72 sets thescheduled waiting time obtained by adding the basic waiting time and apredetermined individual waiting time, after reception of the packetfrom WLAN communication apparatus having a low speed. When the relaycontrol unit 72 has detected the packet forwarding from another WLANcommunication apparatus, belonging to the same partition, through thepacket listening of the communication control unit 71 before thescheduled waiting time elapses, the relay control unit 72 may discardthe packet received at the communication control unit 71. When the relaycontrol unit 72 has not detected the packet forwarding of another WLANcommunication apparatus belonging to the same partition until thescheduled waiting time elapses, the relay control unit 72 makes asetting itself as the relay node, and then may perform the packetforwarding via the communication control unit 71.

According to an embodiment, an individual waiting time may be assignedto each of the WLAN communication apparatuses, for example, according tothe internal transmission priorities, and may be assigned as itsinternal transmission priority*a unit waiting time, where the unitwaiting time may be the same as SIFS. Furthermore, the scheduled waitingtime is the basic waiting time+a individual waiting time, and may be setto 1*SIFS+the internal transmission priority*the unit waiting time=1+theinternal transmission priority*SIFS.

According to an embodiment, the relay control unit 72 may transmit arequested uplink-relay packet to the access point 11, and then afterwaiting for a predetermined basic waiting time, for example, 1*SIFStime, may receive from the access point 11 an ACK packet or a downlinkpacket to be downlink-relayed to the WLAN communication apparatus havinga low speed that has requested the uplink relay.

In this case, when receiving the downlink packet to be downlink-relayed,the relay control unit 72 waits for the predetermined basic waitingtime, for example, 1*the SIFS time, and may perform the relaytransmission of the downlink packet to the WLAN communication apparatushaving a low speed.

Meanwhile, the parameter storage unit 73 stores the transmission timeslot information, the partition information and the internaltransmission priority information that have been received.

FIG. 8 is a conceptual diagram illustrating the downlink transmission ofan access point using multiple transfer rate partitioning andcooperative transmission according to an embodiment of the presentinvention.

Referring to FIG. 8, in a specific beacon period, high speed nodes A, Band C belonging to a specific partition are provided with each ofinternal transmission priorities, respectively, by an access point AP inthe order of the high speed node A, the high speed node B and the highspeed node C.

Commonly, in a WLAN environment, uplink traffic and downlink traffic areused in mixed manner. In other words, the nodes may transmitpredetermined uplink packets to an external network, and may receivedownlink data from an external web server in order to connect with aspecific web site.

Accordingly, the fast WLAN communication method using multiple transferrate partitioning and cooperative transmission according to anembodiment of the present invention attempts to increase the downlinktraffic of the access point AP by giving priority to the downlinktransmission of the access point AP to the specific node whenever theaccess point AP performs uplink transmission from the specific node tothe outside.

In FIG. 8, first, the high speed node A having the highest internaltransmission priority transmits the uplink packet, to be transmitted tothe outside, to the access point AP.

The access point AP, receiving the uplink packet from the high speednode A, determines whether downlink data to be downloaded to the highspeed node A is present in a download queue while waiting for the basicwaiting time, that is, 1* SIFS. Meanwhile, the uplink packet may beoutput to the outside according to a suitable communication protocol ata suitable time.

Since the downlink data to be transmitted to the high speed node A ispresent at the access point AP, the access point AP transmits thedownlink packet to the high speed node A, prior to another node, insteadof waiting for its assigned transmission time slot, after the basicwaiting time, that is, 1*the SIFS waiting time, has elapsed.

Meanwhile, since the high speed node A should first receive an ACKpacket before transmitting an additional uplink packet even when thehigh speed node A has the uplink packet to be additionally transmitted,after transmitting the first uplink packet to the access point AP, thehigh speed node A does not transmit the additional uplink packet beforereceiving the ACK packet, or a downlink packet equivalent to the ACKpacket from the access point AP. Accordingly, there is no concern abouta conflict of the high speed node A with the access point AP, after thehigh speed node A transmitting a first uplink packet and waiting for1*SIFS time.

The high speed node A receives the downlink packet, recognizes thereception of the downlink packet as the reception of a receptionacknowledgement packet responsive to the uplink packet that has beentransmitted by the high speed node A, and then transmits an ACK packetresponsive to the received downlink packet to the access point AP.

The access point AP may remove the downlink data from the download queueafter receiving the ACK packet from the high speed node A.

Accordingly, the access point AP performs downlink transmission in itsown assigned downlink transmission time slot and further performsdownlink transmission, whenever each of the high speed nodes performsuplink transmission, to the corresponding high speed nodes, therebyincreasing the opportunities of transmission and downlink traffic.

The high speed node B having the next highest transmission prioritybecomes aware that uplink transmission of the high speed node A hascompleted without any problem, through the reception acknowledgementpacket, waits for a predetermined random back-off delay time, and thentransmits its own uplink packet to the access point AP.

The access point AP determines whether the downlink data to bedownloaded to the high speed node B is present in the download queuewhile receiving the uplink packet of the high speed node B and waitingfor the basic waiting time, that is, 1*SIFS.

When the downlink data to be transmitted to the high speed node B is notpresent at the access point AP, the access point AP transmits the ACKpacket to the high speed node B after the basic waiting time, that is,1*the SIFS waiting time, has elapsed.

The high speed node B receives a reception acknowledgement packetresponsive to the uplink packet transmitted by itself from the accesspoint AP, and then terminates uplink transmission.

The operations of the high speed node B and the access point AP are notdifferent from common uplink transmission operations.

FIG. 9 is a flowchart illustrating a fast WLAN communication methodcapable of increasing the amount of downlink transmission of the accesspoint using multiple transfer rate partitioning and cooperativetransmission according to an embodiment of the present invention.

Referring to FIG. 9, in accordance with a fast WLAN communication methodcapable of increasing the amount of downlink transmission of the accesspoint using multiple transfer rate partitioning and cooperativetransmission, first, at step S91, the access point 11 may transmit atransmission time slot information, a partition information and aninternal transmission priority information to the high speed nodes 111to 118 and the low speed nodes 121 to 123 in order to enabletransmission time slots, partitions and internal transmission prioritiesto be identified.

The partition information is an information about at least one partitionthat is configured to include at least one node set to the equaltransfer rate, by the access point 11 to group every node 111 to 123connected to the access point 11 according to transfer rates.

The transmission time slot information is an information about at leastone transmission time slot, as one of time intervals available fortransmission within a time period between two consecutive beacon frames,assigned to each of the partitions 21 to 26 grouped according totransfer rates.

The nodes 111 to 113, 114 to 116, 117 and 118, 119 to 121, 122, and 123belonging to partitions, respectively, may transmit respective packetsin the assigned transmission time slot in a contention or non-contentionmanner.

Furthermore, the internal transmission priority information is aninformation about priorities with which the nodes 111 to 113, 114 to116, 117, and 118 belonging to any one of the partitions 21 to 26 maytransmit the packets in the assigned transmission time slot in anon-contention manner.

Meanwhile, at step S92, the access point 11 receives an uplink packetfrom any one node, for example, the high speed node 111.

At step S93, the access point 11 determines whether downlink data to bedownloaded to the high speed node 111 is present in a download queuewhile waiting for the basic waiting time, for example, 1*SIFS.

The process proceeds to step S94 if the access point 11 has the downlinkdata to be transmitted to the high speed node 111, whereas the processproceeds to step S96 if the access point 11 does not have the downlinkdata to be transmitted to the high speed node 111.

If it is determined at step S93 that the downlink data to be transmittedto the high speed node 111 is present at the access point 11, the accesspoint 11 transmits the downlink packet to the high speed node 111 afterthe basic waiting time has elapsed at step S94.

At step S95, the access point 11 may remove the downlink data from thedownload queue if the access point 11 has transmitted the downlinkpacket and, after waiting for the basic waiting time, for example,1*SIFS, received the reception acknowledgement packet from the highspeed node 111.

If it is determined at step S93 that the downlink data to be transmittedto the high speed node 111 is not present at the access point 11, theaccess point 11 transmits the reception acknowledgement packet to thehigh speed node 111 after the basic waiting time has elapsed at stepS96.

FIG. 10 is a conceptual diagram illustrating the downlink relaytransmission of an access point and a relay node using multiple transferrate partitioning and cooperative transmission according to anembodiment of the present invention.

Referring to FIG. 10, downlink traffic related to a source node having alow speed may increase upon cooperative transmission.

A relay node B having a high speed, which has been set as the relay nodefor a source node A having a low speed, may receive an uplink packet tobe relayed from the source node A to the outside, and, after waiting forthe basic waiting time, that is, 1*SIFS, may then transmit the uplinkpacket to the access point AP.

The access point AP receives the uplink packet from the relay node B,and determines whether downlink data to be downloaded to the source nodeA or the relay node B is present in the download queue while waiting forthe basic waiting time, that is, 1*SIFS. Meanwhile, an uplink packet maybe output to the outside according a suitable communication protocol atthe suitable time.

If the downlink data to be transmitted to the source node A or the relaynode B is present at the access point AP, the access point AP transmitsthe downlink packet to the relay node B prior to other nodes after thebasic waiting time, that is, 1*the SIFS waiting time, has elapsed,instead of waiting for its own transmission time slot to come. Incontrast, when the downlink data to be transmitted to the source node Aor the relay node B is not present at the access point AP, the accesspoint AP transmits the ACK packet to the high speed node B after thebasic waiting time, that is, 1*the SIFS waiting time, has elapsed.

Accordingly, the relay node B may receive a downlink packet to bedownloaded from access point AP to the source node A or the relay nodeB, or may receive an ACK packet responsive to the transmitted uplinkpacket after waiting for the basic waiting time, that is, 1*SIFS.

Thereafter, when the relay node B normally receives the downlink packetto be transmitted from the access point AP to the source node A, therelay node B relays the downlink packet to the source node A afterwaiting for the basic waiting time, that is, 1*SIFS.

The source node A receives the downlink packet through the relaying ofthe relay node B, and may then transmit the ACK packet to the accesspoint AP after waiting for the basic waiting time, that is, 1*SIFS. Thisreception acknowledgement packet may be transmitted by the source node Awithout the intervention of the relay node B.

Meanwhile, when the relay node B normally receives the downlink packetto be transmitted from the access point AP to the relay node B, therelay node B may transmit an ACK packet to the access point AP afterwaiting for the basic waiting time, that is, 1*SIFS.

The access point AP may remove the downlink data from the download queueafter receiving the ACK packet from the source node A or the relay nodeB.

FIG. 11 is a flowchart illustrating a fast WLAN communication methodcapable of increasing the amount of downlink relay transmission of theaccess point and the relay node using multiple transfer ratepartitioning and cooperative transmission according to an embodiment ofthe present invention.

Referring to FIG. 11, in accordance with the fast WLAN communicationmethod capable of increasing the amount of the downlink transmission ofthe access point and the relay node having a high speed using multipletransfer rate partitioning and cooperative transmission, first, at stepS111, the access point 11 may transmit a transmission time slotinformation, a partition information and an internal transmissionpriority information to the high speed nodes 111 to 118 and the lowspeed nodes 121 to 123 in order to enable transmission time slots,partitions and internal transmission priorities to be identified.

At step S112, the access point 11 receives an uplink packet from the lowspeed node 123, that is, any one source node, via the high speed node111, that is, the relay node.

At step S113, the access point 11 determines whether downlink data to bedownloaded to the low speed node 123 or the high speed node 111 ispresent in the download queue while waiting for the basic waiting time,for example, 1*SIFS.

The process proceeds to step S114 if the access point 11 has thedownlink data to be transmitted to the low speed node 123 or the highspeed node 111, whereas the process may proceed to step S116 if theaccess point 11 does not have the downlink data to be transmitted to thelow speed node 123 or the high speed node 111.

If it is determined at step S113 that the downlink data to betransmitted to the low speed node 123 or the high speed node 111 ispresent at the access point 11, the access point 11 transmits thedownlink packet to the high speed node 111 after the basic waiting timehas elapsed at step S114.

At step S115, the access point 11, after transmitting the downlinkpacket and receiving the reception acknowledgement packet from the highspeed node 111 or the low speed node 123, may remove the downlink datafrom the download queue.

A reception acknowledgement packet received from the low speed node 123means that a downlink packet is supposed to be transmitted to the lowspeed node 123, or that the high speed node 111 receives a downlinkpacket from the access point 11 and then normally relays the downlinkpacket to the low speed node 123 and, accordingly, the low speed node123 transmits the reception acknowledgement packet.

In contrast, A reception acknowledgement packet received from the highspeed node 11 means that the downlink packet is supposed to betransmitted to the high speed node 111, or that the high speed node 111receives a downlink packet from the access point 11 and then transmitsthe reception acknowledgement packet.

If it is determined at step S113 that the downlink data to betransmitted to the low speed node 123 or the high speed node 111 is notpresent at the access point 11, the access point 11 transmits areception acknowledgement packet to the low speed node 123 or the highspeed node 111 after the basic waiting time has elapsed at step S116.

FIG. 12 is a block diagram illustrating an access point device capableof increasing the amount of downlink transmission using multipletransfer rate partitioning and cooperative transmission according to anembodiment of the present invention.

Referring to FIG. 12, the access point device 120 capable of increasingthe amount of downlink transmission using multiple transfer ratepartitioning and cooperative transmission may include a communicationcontrol unit 1201, a node control unit 1202, a parameter generation unit1203, and a communication module 1204.

The communication control unit 1201 controls transmission and receptionof uplink and downlink between the nodes of internal and externalnetwork via the communication module 1204 according to wired andwireless LAN communication standards. The communication control unit1201 may include a download queue that stores downlink data to betransmitted from the outside to the nodes.

More specifically, when the communication control unit 1201 receives anuplink packet, from the high speed node 111, or from the low speed node123 via the high speed node 111, the communication control unit 1201determines whether downlink data to be downloaded to the low speed node123 or the high speed node 111 is present in the download queue whilethe access point 11 waits for the basic waiting time, for example,1*SIFS. If the downlink data to be transmitted to the low speed node 123or the high speed node 111 is present, the downlink packet istransmitted to the high speed node 111 after the basic waiting time haselapsed.

When the communication control unit 1201 transmits the downlink packetand then receives the reception acknowledgement packet from the highspeed node 111 or the low speed node 123, the communication control unit1201 may remove the downlink data from the download queue.

A reception acknowledgement packet received from the low speed node 123means that the downlink packet is related to data to be transmitted tothe low speed node 123, and further, that the high speed node 111receives a downlink packet from the access point 11 and then normallyrelays the downlink packet to the low speed node 123, and accordingly,the low speed node 123 transmits the reception acknowledgement packet.

In contrast, a reception acknowledgement packet received from the highspeed node 11 means that the downlink packet is related to data to betransmitted to the high speed node 111, and further that the high speednode 111 receives a downlink packet from the access point 11 and thentransmits the reception acknowledgement packet.

If it is determined that the downlink data to be transmitted to the lowspeed node 123 or the high speed node 111 is not present, thecommunication control unit 1201 transmits a reception acknowledgementpacket to the low speed node 123 or the high speed node 111 after thebasic waiting time has elapsed.

Meanwhile, the parameter generation unit 1203 may generate atransmission time slot information, a partition information and aninternal transmission priority information so that the access point 120may identify the transmission time slots, partitions and internaltransmission priorities of the high speed nodes 111 to 118 and the lowspeed nodes 121 to 123.

The node control unit 1202 may transmit the generated the transmissiontime slot information, the partition information and the internaltransmission priority information to the nodes 111 to 123 via thecommunication control unit 1201 and the communication module 1204.

The apparatus according to the present invention can be implemented ascomputer-readable code that can be recorded on a computer-readablestorage medium. The computer-readable storage medium can include alltypes of storage devices on which data that can be read by a computersystem is stored. Examples of the computer-readable storage mediuminclude read only memory (ROM), random access memory (RAM), an opticaldisk, magnetic tape, a floppy disk, a hard disk, and nonvolatile memory,and further include a carrier wave (for example, in the case oftransmission over the Internet). Furthermore, the computer-readablemedium may be distributed throughout computer systems connected over anetwork, and thus computer-readable code can be stored and executed in adistributed manner.

The fast WLAN communication method and apparatus using multiple transferrate partitioning and cooperative transmission according to the presentinvention have the advantage of reducing frequency collisions amongclosely located nodes through multiple transfer rate partitioning.

The fast WLAN communication method and apparatus using multiple transferrate partitioning and cooperative transmission according to the presentinvention have the advantage of selecting a relay node from among aplurality of nodes, in particular, in a high speed transfer ratepartition, thereby the efficiency of cooperative transmission.

The fast WLAN communication method and apparatus using multiple transferrate partitioning and cooperative transmission according to the presentinvention have the advantage of combining a multiple transfer ratepartitioning technique and a cooperative transmission technique havingdifferent purposes and effects together, thereby reducing bothperformance anomaly and frequency collisions.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A method for communicating in a wireless local area network (WLAN), by an access point (AP), the method comprising: receiving a first uplink data frame from a STA; transmitting, to the STA, based on a downlink data to be transmitted to the STA being present, a first downlink data frame in response to the first uplink data frame, receiving a second uplink data frame from the STA in response to the first downlink data frame, and transmitting, based on the downlink data to be transmitted to the STA being not present, to the STA, an acknowledgement frame in response to the second uplink data frame.
 2. The method of claim 1, wherein, based on the first downlink data frame being successfully received by the STA, the successful reception of the first downlink data frame is accepted as a successful acknowledgement of the first uplink data frame by the STA;
 3. The method of claim 2, wherein, based on the second uplink data frame being successfully received by the AP, the successful reception of the second uplink data frame is accepted as a successful acknowledgement of the first downlink data frame by the AP.
 4. The method of claim 2, wherein the first downlink data is transmitted without sending back the acknowledgement frame related the first uplink data frame.
 5. The method of claim 2, wherein based on the acknowledgement frame being transmitted, a frame exchange with the STA is terminated.
 6. The method of claim 2, wherein one or more downlink data frames and one or more uplink data frames are exchanged sequentially between the STA and the AP in a short interframe space (SI FS) interval, and wherein the acknowledgement frame is not transmitted and received by the AP and the STA between the downlink data frame and the uplink data frame.
 7. The method of claim 6, further comprising: allocating a transmission time slot for a group of stations (STAs) including the STA; and transmitting a beacon frame including transmission time slot information and group information.
 8. The method of claim 7, wherein the transmission time slot information indicates a time duration allocated to the group within a beacon interval between two consecutive beacon frames, wherein the group information indicates one or more STAs belonging to the group, and wherein one or more STAs are assigned sub time slot to access a medium in contention within the transmission time slot.
 9. An access point (AP) for communication in a wireless local area network (WLAN), comprising: a communication module; at least one processor; and at least one computer memory operable connectable to the at least one processor and storing instructions that, when executed by the at least one processor, perform operations comprising: receiving a first uplink data frame from a STA; transmitting, to the STA, based on a downlink data to be transmitted to the STA being present, a first downlink data in response to the first uplink data frame, receiving a second uplink data frame from the STA in response to the first downlink data frame, and transmitting, based on the downlink data to be transmitted to the STA being not present, to the STA, an acknowledgement frame in response to the second uplink data frame.
 10. The AP of claim 9, wherein, based on the first downlink data frame being successfully received by the STA, the successful reception of the first downlink data frame is accepted as a successful acknowledgement of the first uplink data frame by the STA.
 11. The AP of claim 10, wherein, based on the second uplink data frame being successfully received by the AP, the successful reception of the second uplink data frame is accepted as a successful acknowledgement of the first downlink data frame by the AP.
 12. The AP of claim 10, wherein the first downlink data is transmitted without sending back the acknowledgement frame related the first uplink data frame.
 13. The AP of claim 10, wherein based on the acknowledgement frame being transmitted, a frame exchange with the STA is terminated.
 14. The AP of claim 10, wherein one or more downlink data frames, and one or more uplink data frames are exchanged sequentially between the STA and the AP in a short interframe space (SIFS) interval, and wherein the acknowledgement frame is not transmitted and received by the AP and the STA between the downlink data frame and the uplink data frame.
 15. The AP of claim 14, wherein the processor is further configured to: allocate a transmission time slot for a group of stations (STAs) including the STA, and transmit a beacon frame including transmission time slot information and group information.
 16. The AP of claim 15, wherein the transmission time slot information indicates a time duration allocated to the group within a beacon interval between two consecutive beacon frames, wherein the group information indicates one or more STAs belonging to the group, and wherein one or more STAs are assigned sub time slot to access a medium in contention within the transmission time slot. 